1. Field of Invention
The invention relates to a light sensing element having two functions and, in particular, to a light sensing element having the two functions of signal control and image capture.
2. Related Art
With the progress in technologies, software and hardware techniques in image scanning devices have great advance. Currently, most image scanning devices have certain scanning quality (i.e. sufficient resolution), which have satisfied the needs of most people and even some professional people. Therefore, the development of image scanning devices will focus on the increasing in image scanning speed and miniaturization of the image scanning system in the future.
When a document (i.e. the original physical object, such as photo or text document) is scanned, a highpower light source is used to generate a strong light beam to illuminate the document to be scanned. Then an encoder obtains a sensed signal by detecting the light beam in present scanned position. The sensed signal is converted by an analog-to-digital converter (ADC) and then is inputted into an application specific processing unit. The application specific processing unit compiles and processes the received signal, and the sensed information is stored in a block of memory. The light sensing element extracts the analog image signal of the scanned document, and outputs a set of analog signals composed of red (R), green (G), and blue (B) color signals. The ADC converts the received analog signal into a digital signal, and then the digital signal is input into the application specific processing unit. After the application specific processing unit processes the digital signal, the processed digital signal is stored in the memory. At an appropriate time, the final image signal is inputted into a processing terminal via an interface converter for other subsequent image processing jobs. In particular, a stepping motor drives a light source or the light sensing element, so that the light sensing element scans the document with a scan line to obtain a document image signal or an image signal. Moreover, the stepping motor performs positioning and adjusts rotation speed thereof based on the sensing information, thereby obtaining better sensing state and speed.
To enhance the scanning quality, a charge-coupled-device (CCD) sensing apparatus with two sensing elements is disclosed in R.O.C. Pat. No. 577226. A first CCD shift buffer having several first CCD elements and several second CCD elements, a first light sensing element set with several first light sensing elements, and a second light sensing element set with several second light sensing elements are disclosed in the patent. The first and second light sensing element sets detect the same light signal and generate respectively first and second signal charges. The charges are received by interleaving first CCD element and second CCD element which are interlaced with each other, thereby achieving high resolution scanning.
However, in this processing mode, the scanning quality of the current image scanning device has satisfied the needs of most users. Hence, how to further improve the conventional image scanning system to achieve a higher scanning speed and/or to minimize the size of the image scanning device, without sacrificing the already satisfactory scanning quality, will be the most important directions in further development of the image scanning device.